1. Technical Field
The present invention relates to a clasp for a band such as a watch band and an accessory band, a watch band using the clasp, and a watch including the watch band.
2. Related Art
As a clasp of belt-like accessories such as a wristwatch band and a bracelet, a three-fold-type clasp is known (for example, refer to JP-A-2000-245512).
The three-fold-type clasp includes a main body portion and a folding portion. The main body portion includes a frame body, a pressing plate, a locking mechanism, and a front cover. The frame body includes a bottom plate and a pair of side walls. The pressing plate is provided so as to be movable in a band-thickness direction with respect to the bottom plate of the frame body. The front cover has a hook portion which engages with the locking mechanism.
The pressing plate is configured to have a spring leaf and a pressurizing plate in an overlapping manner, and a curved spring portion is formed in the spring leaf. When the hook portion is engaged with the locking mechanism, the hook portion pressurizes the spring portion.
The locking mechanism includes a pair of push-buttons, a pair of springs biasing the push-buttons, and a guide housing accommodating the push-buttons and the springs. The guide housing is fixed to side walls of the frame body.
The folding portion is configured to have an intermediate plate and a lower plate. An end portion of the lower plate is pivotably interlocked with the frame body, and a pressurizing projection is provided in the end portion. When a user causes the lower plate to pivot in a direction of being separated from the frame body, the tip of the pressurizing projection is separated from the pressing plate, and the pressing plate is released. Therefore, a band is inserted into a gap between the bottom plate and the pressing plate of the frame body, and the position of the main body portion with respect to the band can be adjusted.
When the user causes the lower plate to pivot in a direction approaching the frame body, the tip of the pressurizing projection pressurizes the pressing plate, and the pressing plate and the band are pressurized toward the bottom plate side. Accordingly, the frame body is fixed to the band. In this case, a side surface portion of the pressurizing projection comes into contact with the guide housing, thereby preventing a lower frame from pivoting beyond thereof.
Moreover, the user folds the intermediate plate toward the lower plate side and causes a spring rod of the intermediate plate to engage with the side walls of the frame body. Accordingly, the intermediate plate and the lower plate can engage with the frame body. The other band is interlocked with the intermediate plate, and the front cover is pivotably interlocked with the intermediate plate as well. The hook portion of the front cover is inserted into an insertion hole of the guide housing and is latched on engagement projections of the push-buttons, thereby being locked. In this case, the hook portion pressurizes the pressing plate via the spring portion and causes the pressing plate to be in press-contact with the band.
Accordingly, the user can adjust an attachment position of the main body portion with respect to the band and can adjust the effective length of the band.
However, in the aforementioned clasp, the main body portion is required to provide with a mechanism of adjusting the effective length of the band, and a mechanism of locking/unlocking the clasp. Accordingly, there are disadvantages such as the complicated structure of the main body portion, the increased number of components, and the increased weight.